/*
symbol.c
Copyright © 2009 William Astle

This file is part of LWASM.

LWASM is free software: you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software
Foundation, either version 3 of the License, or (at your option) any later
version.

This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
more details.

You should have received a copy of the GNU General Public License along with
this program. If not, see <http://www.gnu.org/licenses/>.
*/

/*
for handling the symbol table
*/

#define __symbol_c_seen__

#include <string.h>

#include "lwasm.h"
#include "util.h"

/*
Note that this function may accept symbols that the expression evaluator doesn't
recognize because the expression evaluator must avoid all ambiguity in order
to achieve predictable results. The checks here are simply a fuzz check.
*/
int lwasm_register_symbol(asmstate_t *as, lwasm_line_t *l, char *sym, int val)
{
	lwasm_symbol_ent_t *se, *se2;
	char *p;
	
	int scontext = -1;
	
	// first check if the symbol is valid
	// the following characters are allowed in a symbol:
	// [a-zA-Z0-9._$?@] and any byte value larger than 0x7F
	// although symbols should be restricted to the 7 bit range
	// symbols must start with [a-zA-Z._]
	if (!strchr("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz._@?", *sym))
	{
		register_error(as, l, 1, "Bad symbol: %s", sym);
		return -1;
	}
	
	if (*sym == '@' && isdigit(sym[1]))
	{
		register_error(as, l, 1, "Bad symbol: %s", sym);
		return -1;
	}
	
	for (p = sym; *p; p++)
	{
		if (!strchr("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz._$?@0123456789", *sym))
		{
			register_error(as, l, 1, "Bad symbol: %s", sym);
			return -1;
		}
		// flag local symbols while we're at it...
		if (*p == '?' || *p == '@')
			scontext = as -> context;
	}
	
	// now look it for to see if it is a duplicate
	se = lwasm_find_symbol(as, sym, scontext);
	if (se)
	{
		register_error(as, l, 1, "Mulitply defined symbol: %s", sym);
		return -1;
	}
		
	// if not a duplicate, register it with the value
	se = lwasm_alloc(sizeof(lwasm_symbol_ent_t));
	if (as -> symhead)
	{
		se -> prev = NULL;
		se -> next = as -> symhead;
		as -> symhead -> prev = se;
		as -> symhead = se;
	}
	else
	{
		se -> next = NULL;
		se -> prev = NULL;
		as -> symhead = se;
		as -> symtail = se;
	}
	se -> value = val;
	se -> sym = lwasm_strdup(sym);
	se -> context = scontext;

	return 0;
}

lwasm_symbol_ent_t *lwasm_find_symbol(asmstate_t *as, char *sym, int scontext)
{
	lwasm_symbol_ent_t *se;
	
	for (se = as -> symhead; se; se = se -> next)
	{
		if (scontext == se -> context && !strcmp(sym, se -> sym))
		{
			return se;
		}
	}
	return NULL;
}

// reset the value of a symbol - should not be used normally
// it is intended for use by such operations as EQU
// returns -1 if the symbol is not registered
int lwasm_set_symbol(asmstate_t *as, char *sym, int scontext, int val)
{
	lwasm_symbol_ent_t *se;
	
	se = lwasm_find_symbol(as, sym, scontext);
	if (!se)
		return -1;
	
	se -> value = val;
	return 0;
}